<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>首页</title>
    <link rel="shortcut icon" href="favicon.ico" type="image/x-icon"/>
    <link rel="stylesheet" href="index.css">
    <script src="jquery-3.4.1.js"></script>
    <script>
        $(function() {
          $('h3').css('color', 'blue')
        })
      </script>
</head>
<body>
    div id="app">
  <h3>这是首页内容</h3>
  <img src="kgc.jpg" alt="" width="200">
</div>
</body>
</html>